1. Field of the Invention
The invention relates to a light source device, and especially to a light source device which is used for a projection device, such as a liquid crystal projector or the like.
2. Description of the Related Art
In a light source device which is used for a liquid crystal projector or the like, the light source is a discharge lamp, such as a metal halide lamp or super high pressure mercury lamp. The light radiated from this discharge lamp is focused by a concave reflector, and furthermore, by means of an optical lens, such as an integrator lens or the like, is emitted onto a liquid crystal surface, such that the illuminance on the screen becomes uniform.
There are, for example, discharge lamps of the short arc type as the light source, which during operation, reach a high operating pressure of roughly 20 to 150 atm in the arc tube. In this case, there can also be cases in which, within the conventionally required lamp service life, deterioration of the arc tube or fracture of the discharge lamp occurs. When the discharge lamp fractures, fragments with a high temperature spray in the optical system, in the power source and the like within the projector. These glass splinters adversely affect and foul the above described components. This is disclosed, for example, in published Japanese Patent Application HEI 5-251054. In this case, the repair is complex and great fracture noise may arise.
Known measures against this include a process in which the front opening of the concave reflector is covered with translucent glass, preventing the splinters from spraying to the outside, even if the discharge lamp fractures during operation in the exceptional case. Furthermore, damping the fracture noise by covering with translucent glass and prevention of major fracture noise are also known.
Covering the front opening of the concave reflector with translucent glass is indeed effective for preventing lamp fracture and for noise attenuation. But since the inside of the concave reflector is located essentially in a hermetic state, the inside of the reflector reaches an extremely high temperature during operation. Specifically, the emission part and the hermetically sealed portions of the discharge lamp reach an overly high temperature; this leads to devitrification in the arc tube and formation of cracks in the metal foils in the hermetically sealed portions as a result of oxidation and expansion.
Furthermore, there are cases in which the heat resistance temperature of the film formed by vacuum evaporation is exceeded or in which, between the inside and the outside of the reflector, a large temperature difference occurs when the mirror surface temperature of the reflector becomes unduly high. In these cases, thermal deterioration of the vacuum evaporated film, such as cracks and the like, and large cracks in the reflector due to heat can occur.
Therefore, a primary object of the present invention is to devise an arrangement in which a discharge lamp within a concave reflector and the mirror surface of the reflector can be advantageously cooled, the front opening of the reflector being covered with translucent glass, and the reflector surrounding the discharge lamp.
In a light source device, in which a discharge lamp is attached in the neck of a concave reflector, and which is located in a differential pressure passage system, the above object is achieved in accordance with the invention by the following features.
at least one cooling air discharge opening is located in the neck area of the concave reflector;
translucent glass covers the front opening of the concave reflector; and
at least one cooling air injection opening is located in the area of the front opening of the concave reflector and has directional accuracy with reference to the inside of the concave reflector.
Furthermore, the object is advantageously achieved according to the invention in that the above described air injection opening has a discharge direction which is aligned relative to the hermetically sealed portion on the side of the front opening of the discharge lamp.
Moreover, the object is advantageously achieved in accordance with the invention in that the above described air injection opening has a discharge direction which is aligned such that some of the mirror surface of the concave reflector is directly impacted.
The object is also advantageously achieved in accordance with the invention in that several air injection openings are formed, that at least one of them has a discharge direction which is aligned relative to the hermetically sealed portion on the side of the front opening of the discharge lamp, and that at least one of the remaining air injection openings is aligned such that some of the mirror surface of the concave reflector is directly impacted.
The object is, furthermore, advantageously achieved in accordance with the invention in that some of the peripheral edge of the front opening of the concave reflector is provided with a gap which is provided with an air injection opening.
Additionally, the object is advantageously achieved in accordance with the invention in that the above described air discharge opening and/or the air injection opening is provided with a sound attenuation tube.
Still further, the object is advantageously achieved in accordance with the invention in that in the neck of the concave reflector a sleeve is attached in which a ventilation path is formed which consists of a series of narrow spaces.
The object is also advantageously achieved in accordance with the invention in that the front opening of the concave reflector has a maximum opening diameter of at most 80 mm.
The object is, furthermore, advantageously achieved in that the discharge lamp is operated with a nominal wattage of at least 130 W.